Car Charging Wireless Insufficient Amps?

[evillama]

I'm no electrical engineer so looking to understand the differences in 1A vs. 1.5A or 2.5A car chargers.

I'm using a Qi cradle on a windshield mount and a separate Bluetooth-to-FM transmitter (two fabulous ideas, BTW) so I'm completely wireless in the car - I can use GPS while streaming music on my unlimited data plan. Unfortunately I'm finding that GPS navigation (HERE Drive+) will drain the power faster than it's charging (if I only stream music or news podcasts, the power drain/charge remains balanced).

My main question is though - the Qi charger says it's Output = 1A. Is this a limitation of wireless charging technology, or the adapter I'm using in the cigarette lighter socket? The Bluetooth-to-FM transmitter is always-on, plugged into the socket with a secondary USB charge port of 1.5A. I could get a splitter so I can use another 2.5A charger and plug the Qi into that, but I'm not sure if the "Output = 1A" is the bottleneck of charge into the phone?

In short, what is the true charge power through a Qi plate - is it limited to what the plate says, or what the socket charger says it will output to the phone?

 

[Coreldan]

I've heard people complain the same when using just wired car chargers too that they just arnt quite enough to keep the battery balanced when navigating.

 

[N_LaRUE]

It would have been handy to know what phone you have. If you're on WP8 or WP8.1 etc. But I'll try to help.

If the wireless pad says it's only 1A, that's all it is, you can't increase it. There may be other pads that output more though.

Your adapter to the wireless pad should be sufficient for use. You need to know the input current of the wireless charger as it could be different than the output, possibly higher. Without knowing which pad your using I can't help.

When you're running GPS and Bluetooth you are using a lot of power for a phone. Even playing music is a drain on power. What you should check is to see if the phone charges with either GPS or Bluetooth on. GPS is a big power drain. I've found since upgrading to DP WP8.1 my phone drains significantly faster using GPS.

As for all the connectivity it's best to ensure you have all the power requirements you need. Your socket needs to be able to provide the current you require for both the plate and the transmitter. Then the spliter that you have should be sufficient to power the plate and the FM transmitter.

You need to know the input current of both devices to ensure you are powering them both sufficiently.

Saying all that however my guess is that the phone is draining quicker than that charger can handle. You could see about higher output rating on a charger pad but I would check to see if your phone is simply draining too fast. Get a high current (1.5A) phone charger and test what you're doing to see if the same effect happens. If it does, you then have your answer.

 

[evillama]

Sorry should have mentioned: Nokia 928, Verizon Unlimited Data, WP 8.1 Dev Preview

I have this generic Qi charger:
http://www.ebay.ca/itm/6in1-QI-Wireless-Car-Charging-Charger-Pad-for-Phone-Nokia-Lumia-920-820-/151187239797?ssPageName=ADME:L:OC:US:3160

Using this Bluetooth-to-FM transmitter:
http://www.amazon.com/dp/B00HALPZWU/ref=pe_385040_30332200_pe_309540_26725410_item

The functionality blows away my iPhone and Android friends when they ride in the car with me and see how easy it is to get in and out of the car without dealing with charging wires.

You're right though about the drain - and from the tests I've run, it's solely GPS related. I can stream YouTube, check e-mails, listen to music, be on a phone call, and the battery still charges through the 1A wireless plate, but if I use GPS navigation, it will immediately start to drain the battery even though the charging light is on.

The battery functions should have an alert for when your phone is plugged in but the power is still draining. During long multi-state, 8-hour drives, it doesn't make sense to use the phone as your primary GPS Navigation device if it will eventually empty the phone completely of charge (happened to me on a trip down to Virginia). Would've been better off with a dedicated Garmin or TomTom.

 

[N_LaRUE]

Just a small note. I did check the specs on your wireless charging pad. It requires 1.5A input and your FM transmitter only supplies 1A so you are not at full power with the charger.

Just FYI power in electrical terms in a DC circuit (batteries in this case) is the following formula P=EI where P = power in watts (W), E is voltage (V) and I is current, measured in amps (A). Going simply by that formula you can see that the less current (I) you have the lower the power. When you're dealing with low voltages like this power drops rather steeply with what seems like small current drop. In this case you're losing almost 33% power by simply not having that .5 of an amp.

There's always some allowance for variance in current/voltage in all electrical/electronic devices but steep drops like that will cause problems. Take in that the device is only 70% efficient and you soon realise why the power might be draining faster.

So even with not using the GPS I'd recommend getting something supplies at minimum 1.5A to the charging plate. Preferred 2A, the plate will only take what it needs.

Lastly, since you are one WP8.1DP there are issues with poor battery performance so that is your most likely candidate in this scenario.

 

[evillama]

This is great. Thanks for the thorough investigation and science refresher! First thing I'm going to do is switch to a 2A charger and see what that does with/without GPS use.

 

[N_LaRUE]

This is great. Thanks for the thorough investigation and science refresher! First thing I'm going to do is switch to a 2A charger and see what that does with/without GPS use.

Just another thing I noticed is that the plug that came with your charger states 2.4A. So if you go higher there's no issues. Just keep in mind that the charger will only take what it needs.